Deep fluorine removal agent and method for removing fluorine-containing ions in fluorine-containing wastewater

Abstract

The invention provides a deep fluorine removal agent and method for removing fluorine-containing ions in fluorine-containing wastewater. The deep fluorine removal agent is prepared from the following components in percentage by weight: 40-70% of polyaluminum sulfate, 0.3-30% of hydroxyapatite and the balance of deionized water. When the fluorine removal agent provided by the invention is used for treating the fluorine-containing wastewater, the fluorine removal speed is high, the electric conductivity is reduced, the sludge content is reduced, a relatively good fluorine removal effect can be obtained, and the fluorine ion concentration of the fluorine-containing wastewater treated by the deep fluorine removal agent is lower than 15ppm.

Description

Technical Field

[0001] The invention belongs to the technology of treating fluorine-containing wastewater, and in particular relates to a deep defluorination agent for reducing the fluorine ion concentration and electrical conductivity in water. Background Art

[0002] Semiconductor industrial wastewater is industrial wastewater generated during the wafer production process. When semiconductor factories make wafers, they use a large amount of hydrofluoric acid to clean the wafer surface. In addition to hydrofluoric acid, other acids such as sulfuric acid or phosphoric acid are often mixed in. In the process of liquid crystal display panels and solar energy industries, high-concentration hydrofluoric acid or hydrofluoric acid mixed acid is also used to clean TFT-LCD panels or solar silicon wafers. The pollutants contained in semiconductor industrial wastewater are mainly fluorides and other pollutants.

[0003] At present, the treatment methods of fluoride-containing wastewater are roughly divided into three methods in industry: chemical precipitation, flocculation precipitation, and adsorption. Among them, chemical precipitation is the most commonly used method in industry and has great economic benefits. Generally speaking, calcium salt precipitation is used for high-concentration fluoride-containing industrial wastewater, that is, calcium salts such as calcium chloride or calcium hydroxide are added to the industrial wastewater to make the fluoride ions in the wastewater react with the calcium ions provided by the agent to form calcium fluoride precipitation and then remove the fluoride ions in the water. Although the chemical precipitation method has a simple process, convenient treatment, and small equipment requirements, it derives other problems such as excessive concentrations of chloride ions and calcium ions in the discharged water.

[0004] Please refer to Figure 1 , Figure 1 This is a comparison chart of the concentrations of fluoride ions and calcium chloride after fluoride-containing wastewater is treated by chemical precipitation. The traditional chemical precipitation method is to use calcium salts such as calcium chloride or calcium hydroxide to add calcium salts to fluoride-containing wastewater to react fluoride ions with calcium ions in the wastewater to form calcium fluoride. However, when only calcium salts are used to remove fluoride to a concentration of 50ppm, the removal efficiency will drop significantly. Therefore, it is necessary to add excessive calcium salts for the reaction, resulting in excessive reagents, increased costs, and other problems. As a result, it is necessary to add excessive calcium chloride in the future to reduce the fluoride ion concentration in the wastewater to below 15ppm or even lower in order to meet the discharge water standards, resulting in increased costs, consumption of a large amount of calcium chloride, and environmental pollution. In addition, the addition of excessive calcium chloride will increase the chloride ion content and conductivity in the discharged water, and will also increase the amount of sludge produced.

[0005] Fluoride is difficult to decompose in the natural environment. As the environment's carrying capacity for fluoride is getting lower and lower, the concentration of fluoride ions in the discharged water is becoming more and more stringent. The current discharge water standard stipulated by the Environmental Protection Agency is ≤15ppm. In addition, there are also certain standards for the conductivity of agricultural irrigation water, which must be ≤750μs / cm. Therefore, the present invention has developed a novel deep defluorination agent to overcome the difficulties of the prior art and solve its deficiencies, and solve the problems faced by the industry. Summary of the invention

[0006] In view of the problems in the above-mentioned prior art, the present invention provides a deep defluorinating agent, which is used to treat fluorine-containing wastewater, removes fluoride ions quickly, has a good defluorination effect on fluoride ions in a low concentration range, can reduce the amount of calcium chloride used, and thus reduce the conductivity of the treated fluoride-containing wastewater and the chloride ion concentration in the discharged water, and improves the removal efficiency of fluoride ions in fluoride-containing wastewater to meet the fluoride-containing wastewater discharge standard, thereby increasing recycling and reuse.

[0007] To achieve the above technical objectives, the present invention provides a deep defluorination agent for removing fluoride-containing wastewater, which is composed of the following components in weight percentage concentrations: 40% to 70% polyaluminium sulfate, 0.3% to 30% hydroxyapatite and deionized water supplemented to 100%.

[0008] Preferably, the content of aluminum oxide in the polyaluminum sulfate is 15wt% to 20wt%, and the content of iron oxide is 0.2wt% to 0.8wt%.

[0009] Preferably, the deep defluorination agent is composed of the following ingredients in weight percentage concentrations: 40% to 70% polyaluminium sulfate, 5% to 6.5% polyaluminium chloride, 5% to 30% hydroxyapatite, 1% polyferric sulfate, 1% calcium sulfate, 1% nano-aluminium, 1% nano-iron, 1% nano-calcium and deionized water supplemented to 100%.

[0010] Preferably, the mass fraction of total iron content in the polyferric sulfate is 10% to 20%.

[0011] Preferably, the content of iron oxide in the polyferric sulfate is 0.2 wt% to 0.8 wt%.

[0012] Preferably, the deep defluorination agent has a defluorination efficiency of 90.4% to 99.7%.

[0013] Preferably, the reduction ratio of the conductivity of the fluorine-containing wastewater after being treated with the deep defluorination agent is in the range of 38.3% to 57.0%.

[0014] Preferably, the reduction ratio of the chloride ion concentration of the fluorine-containing wastewater after treatment with the deep defluorination agent is in the range of 33.4% to 80.9%.

[0015] In addition, the present invention further provides a method for removing fluoride ions in fluoride-containing wastewater, which comprises the following steps:

[0016] Dissolving the deep defluorinating agent of the present invention in deionized water, wherein the mixing ratio of the deep defluorinating agent to the deionized water is 1:5-50, so as to prepare a deep defluorinating agent solution with a concentration of 5% to 50% by weight;

[0017] Adjusting the pH value of the fluorine-containing wastewater to 6-8 with liquid alkali; and

[0018] The deep defluorination agent solution is added to the fluorine-containing wastewater after the pH is adjusted, and stirred to react.

[0019] Preferably, the stirring time is 5 to 15 minutes, and the defluorination efficiency of the deep defluorination agent after stirring is 89.3% to 99.7%.

[0020] Preferably, the reduction ratio of the chloride ion concentration of the fluorine-containing wastewater after treatment with the deep defluorination agent is in the range of 33.4% to 80.9%.

[0021] It can be seen from the above description that the present invention has the following advantages:

[0022] The present invention obtains a deep defluorinating agent (also known as MU-RF501) by selecting components with suitable weight percentage concentrations. Whether the defluorinating agent of the present invention is used for high concentration (≥1000ppm) or low concentration (≤50ppm), more than 99% of fluoride ions can be removed by stirring for only 10 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a comparison chart of the concentrations of fluoride ions and calcium chloride after fluoride-containing wastewater is treated using chemical precipitation method.

[0024] Figure 2 It is a comparison chart of chloride ion concentrations of fluoride-containing wastewater after being treated by chemical precipitation method and the deep defluorination agent of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, several embodiments are listed to illustrate the implementation methods of the deep defluorination agent and method for removing fluoride ions in wastewater of the present invention, so those skilled in the art can simply understand the advantages and effects that can be achieved by the present invention through the contents of the following embodiments. It should be understood that the embodiments listed in this specification are only used to illustrate the implementation methods of the present invention, and are not used to limit the scope of the present invention. Those skilled in the art can make various modifications and changes based on common knowledge without departing from the spirit of the present invention to implement or apply the contents of the present invention.

[0026] Example 1: Sources of fluoride-containing wastewater

[0027] The fluorine-containing wastewater is taken from industrial wastewater of a semiconductor factory as the fluorine-containing wastewater to be treated, wherein the pH value of the fluorine-containing wastewater to be treated is between 3 and 4, the fluorine ion concentration is 100 to 1000 ppm, the chloride ion concentration is 5 to 60 ppm, and the conductivity is 1 to 3 ms / cm.

[0028] Example 2: Preparation of deep defluorination agent

[0029] Table 1 shows the components and proportions of the deep defluorination agent of the present invention, and the components are uniformly mixed according to the composition of Table 1. In order to evaluate the efficacy difference of the deep defluorination agent of the present invention at different proportions, the deep defluorination agents of Example 1 and Comparative Examples 1 to 6 are prepared, as shown in Table 1:

[0030] Table 1

[0031] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Polyaluminium Sulfate 40wt% 70wt% 40wt% 40wt% 40wt% 40wt% 40wt% Polyaluminium chloride 6wt% 0wt% 0wt% 6.5wt% 6wt% 5wt% 5.5wt% Hydroxyapatite 10wt% 0.7wt% 0.3wt% 30wt% 20wt% 15wt% 5wt% Polyferric Sulfate 1wt% 0wt% 0wt% 1wt% 1wt% 1wt% 1wt% Nano Aluminum 1wt% 0wt% 0wt% 1wt% 1wt% 1wt% 1wt% Nano Iron 1wt% 0wt% 0wt% 1wt% 1wt% 1wt% 1wt% Nano Calcium 1wt% 0wt% 0wt% 1wt% 1wt% 1wt% 1wt% Deionized water 40.0wt% 29.3wt% 59.7wt% 19.5wt% 30wt% 36wt% 45.5wt%

[0032] Polyaluminum sulfate and polyferric sulfate mainly provide the effects of removing fluoride ions from fluoride-containing wastewater and flocculation; in addition, the matrix of polyaluminum sulfate and polyferric sulfate is sulfate ion, and its solubility in water is the same as that of sulfuric acid in water, which means that the efficiency of polyaluminum sulfate and polyferric sulfate dissolving in water synergistically improves the reactivity with fluoride ions and improves the removal of fluoride ions.

[0033] The content of aluminum oxide in polyaluminum sulfate is in the range of 15wt% to 20wt%, preferably 15.8wt%. The content of iron oxide in polyferric sulfate is in the range of 0.2wt% to 0.8wt%, preferably 0.2wt%. The total iron content (in terms of Fe 3+ The content of the polyol (in terms of weight) is 10 wt% to 20 wt%, preferably 19 wt%.

[0034] Polyaluminium chloride mainly provides the effect of flocculation and removal of fluoride ions.

[0035] The mixing ratio of the deep defluorination agent to the wastewater is 1:150-1000. When the hydroxyapatite in the deep defluorination agent reacts with the fluorine-containing wastewater, the OH in the hydroxyapatite - Ions can react with fluoride ions in fluoride-containing wastewater to achieve the effect of ion exchange. At the same time, hydroxyapatite can also adsorb fluoride ions. Therefore, hydroxyapatite can remove fluoride ions in two ways: ion exchange and adsorption. It can shorten the removal reaction time and reduce the stirring time. The chemical reaction formula of ion exchange is: Ca 10 (PO4)6(OH)2+2F - →Ca 10 (PO4)6F2+2OH - . Thereby further improving the removal rate and effect of fluoride ions. In addition, the OH- ions in hydroxyapatite enter the wastewater after ion exchange, which can maintain the pH value of the wastewater between pH 6 and 8, reduce the amount of liquid alkali (sodium hydroxide) used, and preferably adjust the pH value of the fluoride-containing wastewater to 6 (weakly acidic).

[0036] Example 3: Determination of fluorine removal efficiency of deep defluorination agent

[0037] The mixing ratio of the deep defluorinating agent and deionized water is 1:5-50, so as to prepare a deep defluorinating agent solution with a weight percentage concentration of 5% to 50%. The above dilution ratio can be adjusted according to needs or not diluted, and the present invention is not limited to this. In this example, the deep defluorinating agent prepared in Example 2 is prepared into a solution with a weight percentage concentration of 40% in deionized water and added to the fluorine-containing wastewater to be treated prepared in Example 1, as follows:

[0038] Take seven beakers and add 500 mL of fluorine-containing wastewater to be treated. The technicians in the field of the present invention can measure the pH value according to the existing technology, and adjust the pH value of the fluorine-containing wastewater to between 6 and 8 with sodium hydroxide (liquid alkali), add 0.4 to 1.6 mL of 37 wt% calcium chloride as pretreatment, and in this embodiment, add 0.5 to 2.9 mL of deep defluorination agent prepared according to Example 2, stir for 1, 5, 10, and 15 minutes respectively, let it stand for 5 minutes, extract the supernatant, and use a fluorine electrode to detect the final fluoride ion concentration. The fluoride ion detection method refers to the "Fluoride Salt Detection Method in Water-Fluoride Selective Electrode Method" (NIEAW413.52A), that is, the results are shown in Table 2.

[0039] Table 2

[0040]

[0041] As shown in Table 2, after the deep defluorination agent of the present invention treats the fluorine-containing wastewater of Example 1, the fluorine ion concentration is reduced to 9.5ppm-13.4ppm, and the fluorine removal efficiency is 90.4%-99.7%. Among them, the deep defluorination agent of Example 1 has the best fluorine removal efficiency and the lowest fluorine ion concentration, overcoming the above problems. Figure 1 The traditional chemical precipitation method has exceeded the limit of fluoride removal efficiency, and the fluoride ion concentration in fluoride-containing wastewater is reduced by effectively utilizing minimal reagents, thereby solving the technical problem of the traditional chemical precipitation method requiring the addition of excessive calcium chloride, reducing costs and avoiding the problem of deriving new chemical pollution.

[0042] It can be seen that the deep defluorination agent of the present invention does meet the requirement that the low-concentration fluorine-containing wastewater discharge standard must be lower than 15 ppm.

[0043] Example 4: Determination of conductivity of fluoride-containing wastewater after deep defluorination treatment

[0044] The conductivity of the supernatant of the fluorine-containing wastewater of Example 3 after being treated with a deep defluorination agent for 15 minutes was detected by a conductivity meter, wherein the conductivity detection method refers to the "Method for Determining Conductivity in Water - Conductivity Meter Method" (NIEA W203.51B), and compared with the original conductivity of the fluorine-containing wastewater of Example 1 of 2.65ms / cm, and compared with the traditional chemical precipitation method (i.e., only adding 3 grams of calcium chloride), the comparison results are shown in Table 3.

[0045] Table 3

[0046]

[0047] As shown in Table 3, the deep defluorination agent of the present invention only increases the conductivity of fluorine-containing wastewater to 3.63-4.07 ms / cm, which is 38.3%-57.0% lower than that of the traditional chemical precipitation method. The calculation formula is shown in Mathematical Formula 1, among which the deep defluorination agent of Example 1 has the best effect, the smallest increase in conductivity, and the highest reduction ratio.

[0048]

[0049] Example 5: Determination of chloride ion concentration in fluoride-containing wastewater after deep defluorination treatment

[0050] The supernatant of the fluorine-containing wastewater of Example 3 after being treated with the deep defluorination agent of the present invention for 15 minutes was extracted to detect the chloride ion concentration, wherein the chloride ion detection method refers to the "Chloride Salt Detection Method in Water" (NIEAW407.51C), and compared with the traditional chemical precipitation method (i.e., only 3 grams of calcium chloride was added for comparison), the initial chloride ion concentration of the fluorine-containing wastewater of this example was 55.2ppm, and the results are as follows Figure 2 As shown in Table 4.

[0051] Table 4

[0052]

[0053] like Figure 2 As shown in Table 4, after the fluorine-containing wastewater is treated by chemical precipitation, the chloride ion concentration in the fluorine-containing wastewater is as high as 1557.3ppm. On the contrary, after the deep defluorination agents of Example 1 and Comparative Examples 1 to 6 of the present invention are used to treat the fluorine-containing wastewater, the chloride ion concentration in the fluorine-containing wastewater is only 341.7 to 1055.2ppm, with a reduction ratio of 33.4% to 80.9%, among which the deep defluorination agent of Example 1 has the best effect.

[0054] It can be seen that the deep defluorination agent of the present invention can effectively reduce the conductivity of fluorine-containing wastewater and reduce the chloride ion content in the wastewater while achieving a better defluorination effect, and reduce the amount of sludge generated. Therefore, the deep defluorination agent of the present invention does have a synergistic effect, has environmental and economic benefits, and increases the recyclability of wastewater after defluorination.

Claims

1. A deep defluorination agent for removing fluoride ions in fluoride-containing wastewater, characterized in that: The invention is composed of the following components in weight percentage concentrations: 40% to 70% of polyaluminium sulfate, 0.3% to 30% of hydroxyapatite and deionized water supplemented to 100%.

2. The deep defluorination agent according to claim 1, characterized in that: The content of aluminum oxide in the polyaluminum sulfate is 15wt% to 20wt%.

3. The deep defluorination agent according to claim 1, characterized in that: The invention is composed of the following components in weight percentage concentrations: 40% to 70% of polyaluminium sulfate, 5% to 6.5% of polyaluminium chloride, 5% to 30% of hydroxyapatite, 1% of polyferric sulfate, 1% of calcium sulfate, 1% of nano-aluminium, 1% of nano-iron, 1wt% of nano-calcium and deionized water supplemented to 100%.

4. The deep defluorination agent according to claim 3, characterized in that: The mass fraction of total iron content in the polyferric sulfate is 10% to 20%.

5. The deep defluorination agent according to claim 1, characterized in that: The deep defluorination agent has a defluorination efficiency of 90.4% to 99.7%.

6. The deep defluorination agent according to claim 1, characterized in that: The reduction ratio of the electrical conductivity of the fluorine-containing wastewater after being treated with the deep defluorination agent is in the range of 38.3% to 57%.

7. The deep defluorination agent according to claim 1, characterized in that: The reduction ratio of chloride ion concentration of fluorine-containing wastewater after being treated with the deep defluorination agent ranges from 33.4% to 80.9%.

8. A method for removing fluoride ions from fluoride-containing wastewater, characterized in that: It includes the following steps: Dissolving the deep defluorinating agent according to claim 1 in deionized water, wherein the mixing ratio of the deep defluorinating agent to the deionized water is 1:5-50, so as to prepare a deep defluorinating agent solution with a concentration of 5% to 50% by weight; Use liquid caustic soda to adjust the pH value of fluoride-containing wastewater to 6-8; and The deep defluorination agent solution is added into the fluorine-containing wastewater after adjusting the pH, and stirred to react.

9. The method according to claim 8, characterized in that The stirring time is 5 to 15 minutes, and the defluorination efficiency of the deep defluorination agent after stirring is 89.3% to 99.7%.

10. The method according to claim 8, characterized in that The reduction ratio of chloride ion concentration of fluorine-containing wastewater after being treated with the deep defluorination agent ranges from 33.4% to 80.9%.

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